Scan Sonar Research Articles

A Side Scan Sonar Image Target Detection Algorithm Based on a Neutrosophic Set and Diffusion Maps

To accurately achieve side scan sonar (SSS) image target detection, a novel target detection algorithm based on a neutrosophic set (NS) and diffusion maps (DMs) is proposed in this paper. Firstly, the neutrosophic subset images were obtained by transforming the input SSS image into the NS domain. Secondly, the shadowed areas of the SSS image were detected using the single gray value threshold method before the diffusion map was calculated. Lastly, based on the diffusion map, the target areas were detected using the improved target scoring equation defined by the diffusion distance and texture feature. The experiments using SSS images of single clear and unclear targets, with or without shadowed areas, showed that the algorithm accurately detects targets. Experiments using SSS images of multiple targets, with or without shadowed areas, showed that no false or missing detections occurred. The target areas were also accurately detected in SSS images with complex features such as sand wave terrain. The accuracy and effectiveness of the proposed algorithm were assessed.

Image Distortion Correction Method of 2-MHz Side Scan Sonar for Underwater Structure Inspection

Image Distortion Correction Method of 2-MHz Side Scan Sonar for Underwater Structure Inspection

Combined imaging matching method of side scan sonar images with prior position knowledge

Side scan sonar (SSS) image matching plays an important role in underwater applications, such as combining images to form wide range relief images, underwater simultaneous location and mapping, and construction of images of underwater terrain and objects. Because there are differences between the imaging mechanisms of SSS images and optical images, current matching algorithms for optical images do not always work well for SSS images. This study proposes a combined image matching approach for SSS images. First, the images are preprocessed to remove some environmental effects. Second, feature points that are stable for affine transformations are extracted from the SSS matching images based on speeded-up robust features with prior position knowledge. Third, geometric correction is made by the random sample consensus. After that, a similarity calculation is performed. The proposed approach speeds up the matching process and improves its accuracy by combining feature points matching and similarity calculation. It reduces the mismatching rate and the computation requirement by estimating the location uncertainty with prior knowledge and reducing the searching regions for image matching. Experiments show that the matching algorithm takes less time and has greater reliability and accuracy than traditional algorithms.

Side Scan Sonar based Pose-graph SLAM

Side Scan Sonar based Pose-graph SLAM

A New Method for Acquisition of High-Resolution Seabed Topography by Matching Seabed Classification Images

The multibeam echo sounders (MBES) can acquire accurate positional but low-resolution seabed terrain and images, whereas side scan sonars (SSS) can only acquire inaccurate positional but high-resolution seabed images. In this study, a new method for superimposing corrected-positional SSS images on multibeam bathymetric terrain is proposed to obtain high-resolution and accurate-positional seabed topography using traditional MBES and SSS. Three steps, including the normalization by the z-score, sediment classification by the k-means++ algorithm, and denoising processing using morphological operations, are processed for both MBES and SSS images to obtain the corresponding sediment images. Next, a segmented matching method is given based on the common sediment distributions and features of MBES and SSS sediment images. The two kinds of sediment images are matched segmentally using the speeded up robust features algorithm and random sample consensus algorithm. Then, the positions of SSS images are corrected segmentally using thin plate splines based on matching points. Finally, the corrected SSS image is superimposed on MBES bathymetric terrain, based on positional relationship. The proposed method was verified through experiments, and high image resolution and high position accuracy seabed topography were obtained. Moreover, the performances of the method are discussed, and some conclusions are drawn according to the experiments and discussions.

A wavelet transform based contrast enhancement method for underwater acoustic images

Dredging the surface of the ocean to identify both living and non living things nowadays has become an unproblematic task with the help of the acoustic instruments. Side scan sonar is one of such instruments used for far-reaching the seafloor. The sonar captures the scene of the sea bed by releasing fan shaped sound signal which is then converted to images. These images are normally gray scale low contrast images where the objects cannot be viewed clearly. The proposed method uses the Stationary Wavelet Transform (SWT) to decompose the input image into four components such as Low–Low, Low–High, High–Low and High–High components. The low frequency component is sharpened using Laplacian filter and a mask is created by subtracting the LL component with the filtered image. Then the enhanced LL component is obtained by adding the mask to the input image. The high contrast image is reconstructed by applying inverse stationary wavelet transform which combines the enhanced LL component and the other sub-bands. The results have been compared by replacing the SWT with the Discrete Wavelet Transform by interpolating the frequency components. The quantitative and visual results show that the proposed method using SWT outperforms the state of art techniques in terms of contrast.

Archaeological use of Synthetic Aperture Sonar on deepwater wreck sites in Skagerrak

Marine archaeological surveying in deep waters has so far been challenging, mainly due to operational and technological constraints. The standard tool has been Side Scan Sonar (SSS) towed behind a surface vessel. Synthetic Aperture Sonar (SAS) technology is not subject to the traditional range/resolution trade-off, and produces results of considerably higher quality than traditional SSS. In 2015 and 2016 a comprehensive mapping of wrecks in Skagerrak, a large deepwater area off the south coast of Norway was undertaken, using an interferometric SAS system deployed on an autonomous underwater vehicle. By examining data from two passes of one of the many historical wrecks that were detected in the survey area, we demonstrate how SAS can be used to produce very high resolution imagery and bathymetry of wreck sites. Furthermore, post processing techniques are applied to exploit the high information content inherent in SAS data, enhancing aspects of the data for relevant archaeological analysis and interpretation. We show in this paper how SAS technology represents significant improvements in our abilities to conduct high quality and high resolution seabed mapping. The adoption of this technology will both benefit archaeological research and provide knowledge for better decision making in underwater cultural heritage management.

Underwater 3D Reconstruction Based on Geometric Transformation of Sonar and Depth Information

3D reconstruction is of vital importance to detect and monitor the underwater environment. A method based on geometric transformation of mechanical scanning sonar and depth information is proposed, in which the point cloud data from sonar and depth gauge are acquired to reconstruct the underwater 3D environment. However, noise and interference can affect the measurement of sonar, and movement of sonar during measurement can lead to distortion of the received data. Meanwhile, translation and rotation movement of sonar head may happen when ROV dives which can lead to different body reference coordinates of different scanning. To solve this, pre-processing and motion compensation are implemented at first, and underwater matching correction algorithm is used to calculate the translation and rotation of the sonar head. Then the inverse operation is implemented to convert the scan data of every depth into the same coordinate reference system. Finally, surface reconstruction of point clouds from sonar the depth information are used to reconstruct underwater environment based on MLS (Moving Least Square Method) using PCL (Point Cloud Library). Water tank experiments verify the effectiveness of the proposed method.

무인수상정의 기뢰 탐지 임무 수행을 위한 통합 시뮬레이션 방법 연구

The USV performs various missions including mine detection and marine reconnaissance and survey unmanned. As the autonomic software for USV takes charge of detection, decision, and command instead of human, the verification and validation (V&V) of the software is highly required at the early design stage. Due to the difficulty of such V&V before the real USV is made, the virtual prototype of USV and ocean space are adopted in this study. For mine detection mission, which is one of the most important mission of USV, four modules are developed and implemented here; scenario management and display module, USV motion analysis module, submarine topography synthesis module, and mine detection module. The mine detection module represents the control algorithm in autonomic software, and the rest of the modules are virtual prototype which represents the ocean space and hardware in USV such as GPS (Global Positioning System) and SSS (Side Scan Sonar). With the virtual prototype modules, the control algorithm in mine detection module is verified. Meanwhile, for the data communication between the modules, the ROS (Robot Operating System) is used. The ROS provides message communication function between the modules, so that each module can transmit and receive data during the simulation. To check the applicability of the proposed method, the mine detection scenario is performed using the virtual prototype of USV and ocean space. The result shows that the proposed method can be effectively used to test and develop the mine detection algorithm of autonomic software in USV.

Seabed Detection Using Application Of Image Side Scan Sonar Instrument (Acoustic Signal)

The importance of knowing the method for seabed detection using side-scan sonar images with sonar instrument is a much-needed requirement right now. This kind of threat also requires frequent sonar surveys in such areas. These survey operations need specific procedures and special equipment to ensure survey correctness. In this paper describes the method of observation and retrieval of marine imagery data using an acoustic signal method, to determine a target based on the sea. Side scan sonar is an instrument consisting of single beam transducer on both sides. Side scan sonar (SSS) is a sonar development that is able to show in two-dimensional images of the seabed surface with seawater conditions and target targets simultaneously. The side scan sonar data processing is performed through geometric correction to establish the actual position of the image pixel, which consists of bottom tracking, slant-range correction, layback correction and radiometric correction performed for the backscatter intensity of the digital number assigned to each pixel including the Beam Angle Correction (BAC), Automatic Gain Control (AGC), Time Varied Gain (TVG), and Empirical Gain Normalization (EGN).

Inversion of Side Scan Sonar Motion and Posture in Seabed Geomorphology

Abstract Side scan sonar measurement platform, affected by underwater environment and its own motion precision, inevitably has posture and motion disturbance, which greatly affects accuracy of geomorphic image formation. It is difficult to sensitively and accurately capture these underwater disturbances by relying on auxiliary navigation devices. In this paper, we propose a method to invert motion and posture information of the measurement platform by using the matching relation between the strip images. The inversion algorithm is the key link in the image mosaic frame of side scan sonar, and the acquired motion posture information can effectively improve seabed topography and plotting accuracy and stability. In this paper, we first analyze influence of platform motion and posture on side scan sonar mapping, and establish the correlation model between motion, posture information and strip image matching information. Then, based on the model, a reverse neural network is established. Based on input, output of neural network, design of and test data set, a motion posture inversion mechanism based on strip image matching information is established. Accuracy and validity of the algorithm are verified by the experimental results.

Inexpensive Video Drop-camera for Surveying Sensitive Benthic Habitats: Applications from Glass Sponge (Hexactinellida) Reefs in Howe Sound, British Columbia

Where marine waters are shallow and bathymetric features are steep, the typically employed multi-beam side scan sonar is not always reliable for identifying complex biological structures. Here, we present a cost-efficient method used in Howe Sound, British Columbia, for bathymetric mapping, exploration, and ground-truthing of glass sponge bioherms. A simple depth sounder and software package was used to produce bathymetric maps. From these maps, prospective sites were selected and surveyed to investigate bioherm presence with a simple drop-camera towed off the bow of a small drifting vessel during calm seas. This method was used during a 4-year citizen science initiative that led to the discovery of 12 glass sponge bioherms in Howe Sound, the first step in protecting these globally unique reefs from the impact of bottom-contact fishing, anchoring, and potential industrial contamination. Before our work using this method, only two glass sponge bioherms had been identified in Howe Sound. The method also proved effective as a means to quantify damage to bioherms from fishing gear.

Research on Underwater Navigation Algorithm Based on SIFT Matching Algorithm

Autonomous Underwater Vehicle (AUV) is currently used to side scan sonar, doppler velocimetry and inertial navigation devices and other equipment-based integrated navigation program navigation. The side scan sonar can generate the underwater acoustical image in real time and match it with the feature database through the image matching algorithm to filter the navigation data. Aiming at the characteristics of underwater acoustic image data, the method of drawing underwater acoustic image is described. In order to integrate the feature matching of the underwater acoustic image into the integrated navigation, this paper introduces the SIFT feature matching algorithm to improve the characteristics of the underwater acoustic image and introduces the discriminant condition based on the least squares method. After the matching criterion is introduced, the improved SIFT feature matching algorithm is greatly improved when the landmark matching is achieved, and the occurrence of false matching is avoided. Finally, the real experimental data obtained by the side-scan sonar equipment are verified by the algorithm, and the satisfactory results are obtained.

Mapping of sound scattering objects in the northern part of the Barents Sea and their geological interpretation

On cruises 25 (2007) and 28 (2011) of the R/V Akademik Nikolai Strakhov in the northern part of the Barents Sea, the Geological Institute, Russian Academy of Sciences, conducted comprehensive research on the bottom relief and upper part of the sedimentary cover profile under the auspices of the International Polar Year program. One of the instrument components was the SeaBat 8111 shallow-water multibeam echo sounder, which can map the acoustic field similarly to a side scan sonar, which records the response both from the bottom and from the water column. In the operations area, intense sound scattering objects produced by the discharge of deep fluid flows are detected in the water column. The sound scattering objects and pockmarks in the bottom relief are related to anomalies in hydrocarbon gas concentrations in bottom sediments. The sound scattering objects are localized over Triassic sequences outcropping from the bottom. The most intense degassing processes manifest themselves near the contact of the Triassic sequences and Jurassic clay deposits, as well as over deep depressions in a field of Bouguer anomalies related to the basement of the Jurassic–Cretaceous rift system

Coralligenous morphotypes on subhorizontal substrate: A new categorization

Coralligenous has a relevant role in submarine landscape formation and demise through geological times, producing various morphotypes on the seafloor. Several terms are used to define coralligenous morphotypes, but their application through different geological and environmental settings still remains inconsistent. Through a systematic analysis of seafloor acoustic remote data (multibeam, side scan sonar and subbottom profiler) along Apulia continental shelf, ground-truthed by video observations and direct sampling, we detected a number of coralligenous morpho-acoustic facies as 0.2 up to 4m topographic reliefs with steep flanks and a rigid inhomogeneous biogenic framework, characterized by medium to strong SSS backscatter and a variable plan-view geometry. The observed pattern led to the identification of coralligenous meso- and macrohabitat in which the biogenic frameworks (i.e. coralligenous) prevail as sole biocommunity on the seafloor or are associated with other type of habitats: (i) coralligenous sensu stricto, (ii) coralligenous and detritic bottom, (iii) coralligenous and muddy bottom, (iv) coralligenous and Posidonia meadow. Finally we improve the geomorphological definition of bank, proposing this new descriptive rigorous categorization for coralligenous morphotypes on sub-horizontal substrate: 1) tabular bank, 2) discrete relief, and 3) hybrid bank.

The Two-Dimensional Wavelet Transform De-noising and Combining with Side Scan Sonar Image

This paper puts forward an image de-noising method based on 2D wavelet transform with the application of the method in seabed identification data collection system. Two-dimensional haar wavelets in image processing presents a unified framework for wavelet image compression and combining with side scan sonar image. Seabed identification target have 7 target detection in side scan sonar imagery result. The vibration signals were analyzed to perform fault diagnosis. The obtained signal was time-domain signal. The experiment result shows that the application of 2D wavelet transform image de-noising algorithm can achieve good subjective and objective image quality and help to collect high quality data and analyze the images for the data center with optimum effects, the features from time-domain signal were extracted. 3 vectors were formed which are v1, v2, v3. In Haar wavelet retained energy is 93.8 %, so from the results, it has been concluded that Haar wavelet transform shows the best results in terms of Energy from De-noised Image processing with side scan sonar imagery.

Paradigm shift of underwater echo sounding technology III—Evaluation of paradigm shift echo-sounder

Underwater echo sounding technology was developed 65 years ago and has been applied to various systems such as fishfinder, bathymetry, sonar, side scanning sonar, multi beam echo sounding system and synthetic aperture sonar. We have suggested a new concept that may change the history of underwater echo sounding technology, should be called as “Paradigm Shift.” In the conventional system, the transmission intervals are always longer than the time of the round trip distance to the target divided by the underwater sound velocity. By adapting our new “Paradigm Shift Echo-sounder” into the system, the transmission intervals can be decided except for depending on a target and it will be possible to conduct a bathymetry survey that transmits 100 times per second. The system utilized the 7th order Gold code sequence signals. Transmitting signal is the phase modulated and four cycles of carrier signals as one bit of the Gold code sequence. The actual sea trial experiment was done by the proto type of “Paradigm Shift Echo-sounder.” The experimental result was obtained by the transmission of 100 times per second at the depth of 10 to 80 m sea bottom. We also confirmed that this system could reconstruct a high-resolution echogram of the artificial reef.

Historical development of side scan sonar

The seabed mapping side scan sonar, conceived and developed in the 1950s at the U.S. Navy Mine Defense Laboratory (USNMDL) [Commander and Sternlicht, J. Acoust. Soc. Am. 137, 2307 (2015)], was inspired by the Royal Navy ASDIC Type-162, a late-WWII hull mounted side-looking sonar capable of recording the silhouettes of bottomed U-boats. The commissioned U.S. Navy C-MK-1 SHADOWGRAPH, which operated in the Megahertz band and employed curved apertures for cross-track focusing, represents the first in a long history of military and commercial innovations. Commercial side scan sonars, typically operating in the tens or hundreds of Kilohertz, reached the marketplace in the 1960s. The SHADOWGRAPH series led to the Navy’s AN/AQS-14 and French DUBM-series mine detection sonars, and the active tow vehicles of the C-MK-1 served as test platforms for the first synthetic aperture sonars (SAS) fielded at USNMDL (now the Naval Surface Warfare Center Panama City Division) during the 1970s. Through the present day these systems, military and commercial, have been augmented by revolutionary: developments in swath bathymetry side scan sonar, multi-beam echo sounders, and SAS; signal processing advances in acoustic tomography and spectroscopy; and information processing advances in environmental characterization, automatic target recognition and seabed change detection.

T/B APEX 3508: Best Practices for Detection and Recovery of Sunken Oil

ABSTRACT On September 2, 2015, two towing vessels collided on the Lower Mississippi River at Mile 937, near Columbus, Kentucky, resulting in the complete breach of the #3 starboard cargo tank on the T/B APEX 3508 and the release of 120,588 gallons of clarified slurry oil (CSO; Group V oil; Specific Gravity: 1.14) into the navigable waterway. The incident was classified as a Major Inland Spill in accordance with the National Oil and Hazardous Substance Contingency Plan and a Major Marine Casualty that was jointly investigated by the United States Coast Guard and the National Transportation Safety Board. Over flights conducted as far as 20 miles downriver indicated only light, sporadic sheening for 1–2 days. On-water and shoreline assessments conducted up to six miles downriver revealed no visible signs of surface oiling. Based on its properties, the vast majority of the CSO was presumed to have sunk, but its precise disposition and location was not confirmed. Using side scan sonar (SSS) technology, two distinct subsurface anomalies with an approximate combined area of 9,200 m2 were identified on the river bed in the vicinity of the incident. The anomalies were confirmed as oil by divers and direct sampling, and were then divided into 25 m grids for identification and tracking. The Unified Command evaluated best available technologies and determined that GPS guided environmental dredging would be the safest, most effective and efficient of the recovery options. The established cleanup endpoint was a maximum of 10% sporadic oil distribution in each grid. Two endangered mussel species were identified as potentially inhabiting the affected area. A diver survey was conducted in the area and concluded that bottom habitat was not likely to support the listed species. Further consultations with the resource manager indicated that proposed recovery operations posed low risk to the species. Recovery operations commenced on September 15, 2015 and concluded on September 25, 2015. Endpoint verification was conducted via SSS. In total, response operations lasted 23 days (eight operational periods), involved over 120 responders and 75 specialized response assets, and cost approximately $5 million. Approximately 2,524 m3 of dredged material (liquid and solids) were removed. After decanting, approximately 1,730 m3of oiled solids representing approximately 50 to 75% of the spilled product was recovered. This case serves as a benchmark for sunken oil detection and recovery operations, and identified many best practices that should be considered on future cases with similar spill conditions.

Seafloor mapping with a cylindrical array

Seafloor mapping is conducted with different types of arrays. Single beam mapping systems are often constructed with piston arrays. Linear arrays are used for both side scan sonar and for multibeam echo sounders. These conventional approaches to seafloor mapping are typically constrained to a single observation of any one point on the seafloor for any one pass of a moving vessel. A less conventional cylindrical array offers the opportunity to observe the majority of the seafloor from different perspectives but with the same angle with a single pass. This has the potential to improve the resulting depth estimates and seafloor backscatter products. In 2016, a Simrad Omnisonar was used to demonstrate seafloor mapping with a cylindrical array. While this array is designed for observing fish schools, a small area was successfully mapped and the results compared with a conventional bathymetric mapping system. Observations on the benefits and challenges of this approach to seafloor mapping will be discussed.